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1
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter and granulated sugar on medium speed until light and fluffy, about 3 minutes, scraping down the sides of the bowl as needed.
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2
Add the egg and vanilla, and beat to combine.
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3
Add the flour and salt; mix on low speed until combined.
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4
Turn out the dough onto a clean work surface.
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5
Divide in half and roll each piece into a log about 1 1/2 inches in diameter.
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6
Wrap in parchment paper, making sure to cover ends completely, and place in empty paper-towel tubes, if using.
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7
Refrigerate until firm, at least 1 hour or overnight.
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8
Preheat the oven to 350F, with racks in the upper and lower thirds.
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9
Line two large baking sheets with parchment paper.
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10
Let dough stand at room temperature until soft enough to slice, about 15 minutes.
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11
Roll dough logs in sanding sugar, coating them evenly, and slice into 1/4-inch-thick rounds.
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12
Place about 1 inch apart on prepared sheets.
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13
Bake, rotating sheets halfway through, until golden brown around the edges, 15 to 20 minutes.
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14
Transfer cookies to a wire rack to cool completely.
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15
Finely chop 4 ounces bittersweet chocolate (3/4 cup).
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16
Sift out fine dust and discard.
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17
Follow instructions for the Icebox Butter Cookies, adding chopped chocolate along with the flour.
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18
Finely chop 4 ounces (1/2 cup) lightly toasted pecans or pistachios.
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19
Sift out fine dust and discard.
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20
Follow instructions for the Icebox Butter Cookies, adding chopped nuts along with the flour.
